“William Wilson,” episode 43 of HBO’s “Boardwalk Empire,” refers to an Edgar Allan Poe short story about a college student who in effect commits suicide by murdering his doppelganger.

Analyzing the cautionary tale proves too much for freshman William Thompson (Ben Rosenfield). Guilt-stricken after accidentally killing a classmate and then letting an innocent person go to jail, Willie storms out of class.

By turning his back on education and turning to gangster Nucky Thompson (Steve Buscemi) for employment, Willie squanders his chance of earning honest wages in the corrupt Prohibition era.

When speaking with Willie later, Nucky emphasizes the importance of keeping one’s wits while in the cutthroat bootlegging biz. “This isn’t a game, Will. I need to trust you,” he says.

Nucky also has trust issues with Prohibition Agent Warren Knox (Brian Geraghty). Warren claims to be on the take but secretly works with Bureau of Investigation Director J. Edgar Hoover (Eric Ladin) to try to topple Nucky’s interstate criminal network.

To learn more about the agent, Nucky queries Gaston Means (Stephen Root), a slimy special investigator with the Department of Justice. Gaston feigns ignorance, however, because he avoids prison by secretly acting as an informant for Warren.

Daughter is supposed to spy on Chalky and report back to heroin kingpin Valentin Narcisse (Jeffrey White), who’s plotting to seize the nightclub. But Valentin strangled Daughter’s prostitute mom long ago, and Chalky might be the key to revenge.